What sort of guidelines do people follow when deciding on theminra setting? At one end of the spectrum, you have broadcast video streaming servers that deal exclusively with long, sequential reads. At the other end, you have something like an INN server storing articles in individual files. Are there any tools to help decide which setting is best, or do you just "eyeball" it and try both settings and see which one seems better?
My simple rule is minra=on for crazy apps like INN what have tons of small totally random I/O's and minra=off for almost anything else. Basically, if you think caching will help you in any way you want minra off.
A single drive should be able to sustain 8MB/sec or higher just onits own... a stripe of five drives should hit at least 40MB/sec. sysstat on that filer does in fact report 38 to 43MB/sec disk reads during a "vol scrub".
Actually, the 9GB SCSI drives I believe you're using are only rated for a max (not sustained) external transfer rate of 5MB/sec, so the numbers you're seeing really make sense to me. FYI, the max external transfer (not sustained) rate for our 18GB FC-AL drives is a much nicer 12.5MB/sec so you would probably see better (although not necessarily double <g>) sequential performance with those....
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